ARE PROBIOTICS WORTH THE HYPE FOR ATHLETES?

Infographics and charts included.

Written By: 

By Astrid Zuluaga Lopez, Dietetic Intern for Texas Womans University

Edited by Meredith Sorensen, MS, RD, LD Memorial Hermann Sports Medicine Institute

The gut microbiome which contains all types of gastrointestinal bacteria has become a topic of interest in recent years due to the potential benefits on athletic performance. Interestingly enough, the microbiome of the athletic population is even more diverse than that of the general adult population^1,2. This diversity found in the professional athlete’s gut flora may in part be due to having a higher awareness of adequate body fueling techniques and proper nutrition throughout the many years of training compared to their non-athlete counterparts³. Exercise supports bacteria proliferation, regulates mood, decreases fatigue, and strengthens the immune system^1,3.

Why is gut health important to athletes? 

When the training schedule of an athlete intensifies and the athlete becomes overtrained, it can put the athlete’s gastrointestinal (GI) tract under stress. The GI tract is in tune with the immune system as 70-80% of immune cells in our body are present in the gut⁴; therefore, a negative or weak immune response to a pathogen, can debilitate the athlete and consequently, affect their performance. This lack of efficient immune response against infection can be due to exercise-induced immunosuppression which tends to happen when exercising intensity, duration, and training load increase exponentially. Overtraining during competition season isn’t uncommon as athletes are pushing themselves over their limits to achieve and maintain high levels of fitness in order to keep up with the demand of their sport and with the other competitors. For this reason, managing adequate nutrition, sleep, and rest time in a strategic manner with a sports medicine team may reduce the chances of athletes becoming prone to upper respiratory infections (URTIs) due to exercise-induced immunosuppression.

Through the years, the relationship between strenuous exercise and URTIs has been studied yielding inconclusive results; nevertheless, more recent studies have demonstrated that the immune system of endurance-trained athletes does become suppressed during high-intensity training and can last from several hours to days which could leave the body susceptible to infection^3,5. For this reason, athletes nowadays consider an array of nutritional supplements, including probiotics, to support their health sometimes as a preventative measure and other times to potentially optimize athletic performance.

Probiotics and their Impact on Athletic Performance

Probiotics are defined as “living organisms which, when administered in adequate amounts, confer a health benefit on the host⁶. Not to be confused with prebiotics which are non-viable substances that probiotics use to improve macronutrient absorption and gut health⁶.

 A lot of the statistically significant benefits found regarding the impact of probiotics on athletic performance are related to their role in the immune system as evidenced in the reduction in recovery time, decrease in GI discomfort, and the lowering of the incidence of URTIs in endurance athletes³. Nonetheless, it is important to consider that these potential benefits are largely strain- and dose-dependent³. 

How do probiotics work in our body? 

The mechanism of action of probiotics and their influence on the immune system of athletes is poorly understood; however, it has been demonstrated that probiotics may have the ability to decrease low-grade inflammation, increase resistance to URTIs, reduce the duration of URTIs, and suppress intestinal inflammation^3. It is believed that this is due to probiotics’ role in improving the number of immune-presenting cells in our system. An example of this would be salivary immune cells which are considered the first line of defense against pathogens, and their ability to fight infected cells⁸.

What’s the best probiotic strain to support endurance athletes’ immune system?

The most studied and commercially available strains of probiotics are found within the Lactobacillus and Bifidobacterium genera³. Table 1 provides more information about the specific strain of probiotics where immune response enhancement was reported. 

However, it is important to note that a set of recommendations for probiotic consumption in athletes has NOT been established due to the variability in research findings. For this reason, athletes are first encouraged to discuss potential probiotic supplementation with a sports dietitian and physicians of their sports medicine team to evaluate whether or not its consumption is essential to the athlete. Then, consider supplementation of probiotic strains with evidence-based dosages as these have been observed to show benefits in the immune system and could positively impact athletic performance. 

TABLE 1

Is it safe to consume probiotics? 

A great number of studies have shown that the adverse effect of probiotics in athletes has been minimal, indicating that their use is safe. Nevertheless, athletes are advised to carefully choose commercially available probiotics products by ensuring that the strain type, evidence-based dosage, unit measure (CFU), and a third-party verification stamp³ are present in the product for quality and safety purposes, and prevention of the intake of unknown substances. Moreover, the regular consumption of probiotics is necessary in order to take advantage of its benefits. It is recommended that athletes consume probiotic supplementation for a minimum of 14 days prior to the start of competitions or important events to allow for colonization of bacteria in the gut ^3,12. Lastly, probiotics can also be found in food sources such as yogurt, kombucha, grains, and fiber-rich foods. It is ideal that athletes consider ingestion of probiotics from food sources before aiming for a supplemental source¹². 

The take-home message

Probiotics may improve the immune response of endurance athletes against URTIs. This could consequently result in fewer chances of becoming ill which would allow the athlete to not miss training, maintain exercise intensity, and spend less time in the recovery phase, especially during competition season when athletes are more susceptible to infection due to exercise-induced immunosuppression. Nevertheless, as more data about probiotics’ safe and effective implementation in athletes emerges, understanding the current limitations in research is imperative. The variability of the findings which prevents the establishment of recommendation guidelines and regulatory measures for the consumption of probiotics is a factor to be considered during the interpretation of future research studies, selection of supplement products, and claims about its benefits in athletic performance.  

Have questions? Please feel free to talk to an Athlete Training and Health Performance Coach or Meredith Sorensen, Sports Dietitian, MS, RD, LD with the Memorial Hermann Rockets Sports Medicine Institute. Meredith can be reached at Meredith.Sorensen@memorialhermann.org or can be found on Instagram at @meredithdarcienutrition. 

References

1. Wosinska, L., Cotter, P. D., O’Sullivan, O., & Guinane, C. The Potential Impact of Probiotics on the Gut Microbiome of Athletes. Nutrients. 2019;11(10), 2270. https://doi.org/10.3390/nu11102270

2. Sivamaruthi, Kesika, & Chaiyasut. Effect of Probiotics Supplementations on Health Status of Athletes. International Journal of Environmental Research and Public Health. 2019;16(22), 4469. https://doi.org/10.3390/ijerph16224469

3. Jäger, R., Mohr, A.E., Carpenter, K.C. et al. International Society of Sports Nutrition Position Stand: Probiotics. J Int Soc Sports Nutr. 2019;16, 62. https://doi.org/10.1186/s12970-019-0329-0

4. Wiertsema, S. P., van Bergenhenegouwen, J., Garssen, J., & Knippels, L. M. J.The Interplay between the Gut Microbiome and the Immune System in the Context of Infectious Diseases throughout Life and the Role of Nutrition in Optimizing Treatment Strategies. Nutrients. 2021;13(3), 886. https://doi.org/10.3390/nu13030886

5. Cicchella, A., Stefanelli, C., & Massaro, M. Upper Respiratory Tract Infections in Sport and the Immune System Response. A Review. Biology. 2021;10(5), 362. https://doi.org/10.3390/biology10050362

6. Hill, C., Guarner, F., Reid, G., Gibson, G. R., Merenstein, D. J., Pot, B., Morelli, L., Canani, R. B., Flint, H. J., Salminen, S., Calder, P. C., & Sanders, M. E.The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology & Hepatology. 2014; 11(8), 506–514. https://doi.org/10.1038/nrgastro.2014.66

7. Thea Scantlebur, & Gibson. Prebiotics. Best Practice & Research Clinical Gastroenterology. 2004; 18(2), 287–298. https://doi.org/10.1016/j.bpg.2003.10.008

8. Gleeson, M., Bishop, N. C., Oliveira, M., & Tauler, P. Daily Probiotic’s (Lactobacillus casei Shirota) Reduction of Infection Incidence in Athletes. International Journal of Sport Nutrition and Exercise Metabolism. 2011; 21(1), 55–64. https://doi.org/10.1123/ijsnem.21.1.55

9. Cox, A. J., Pyne, D. B., Saunders, P. U., & Fricker, P. A. Oral administration of the probiotic Lactobacillus fermentum VRI-003 and mucosal immunity in endurance athletes. British Journal of Sports Medicine. 2008;44(4), 222–226. https://doi.org/10.1136/bjsm.2007.044628

10. Michalickova, D., Minic, R., Dikic, N., Andjelkovic, M., Kostic-Vucicevic, M., Stojmenovic, T., Nikolic, I., & Djordjevic, B. Lactobacillus helveticus Lafti L10 supplementation reduces respiratory infection duration in a cohort of elite athletes: a randomized, double-blind, placebo-controlled trial. Applied Physiology, Nutrition, and Metabolism. 2016; 41(7), 782–789. https://doi.org/10.1139/apnm-2015-0541

11. Shephard, R. Reversal in fatigued athletes of a defect in interferon γ secretion after administration of Lactobacillus acidophilus. Yearbook of Sports Medicine. 2007; 136–138. https://doi.org/10.1016/s0162-0908(08)70120-x

12. AIS Sports Supplement Framework Probiotic Supplement. Australian Institute of Sport. 2021